In a long distance water pipeline, air accumulated in the pipeline will reduce filling efficiency of the pipeline, or even make filling of the pipeline impossible to be successfully completed. Therefore, a high-speed intake and exhaust valve (air valve) is required to remove air in the pipe while filling the pipeline with water.
And the current high-speed intake and exhaust valve (air valve) mainly uses:
(i) Direct motion type or floating ball operation type high-speed intake and exhaust valve (air valve), will automatically exhaust a large amount of air when filling the blank pipe with water or suction a large amount of air when emptying the pipeline system; and under a condition that the system is filled and pressure exists, it will keep a closed state and never open again. However, its closing member can be easily seized by high-speed airflow during a high-speed exhaust process, and then suddenly blocks the exhaust vent, which leads to a blowing-block phenomenon or an air-block phenomenon. Once blowing-block occurs (i.e. the exhaust valve (air valve) closes), it will stay in the closed state for a long time. Even if the pipe is filled with air that needs to be exhausted, the air valve will not open for exhaust again. It will also cause the generation of a valve-closing water hammer of the air valve when blowing-block occurs.
(ii) Combined exhaust valve (air valve), adds a trace exhaust valve (air valve) on the basis of the direct motion type or floating ball operation type high-speed intake and exhaust valve (air valve). The combined exhaust valve can exhaust a trace amount of air under the condition that the system is filled and pressure exists, but cannot exhaust completely, cannot exhaust whenever air presents, sprays water while exhausting air, and has loose sealing. It cannot inhibit a cavity-closing water hammer and the valve-closing water hammer.